KR20180123087A - Heat-resistant fiber structure - Google Patents

Abstract

The heat-resistant fiber structure comprises heat-resistant fibers having a glass transition temperature of 100 ° C or higher, and the heat-resistant fibers are bonded to each other.

Description

Heat-resistant fiber structure

The present invention relates to a heat-resistant fiber structure made of heat-resistant fibers and used as a heat insulating material and a sound-absorbing material, and a method of manufacturing the same.

BACKGROUND ART [0002] Conventionally, fiber materials using heat-resistant fibers have been used as heat insulating materials, sound absorbing materials, and the like in the fields of vehicles, aircraft, and construction.

A fiber material such as a fiber structure used for such a purpose is required to have low density from the viewpoint of light weight and also requires strength such as bending stress and tensile strength. In particular, strength under high temperature conditions becomes important. For example, strong strength at high temperatures is strongly demanded in a sound-absorbing thermal insulating material embedded in a wall of an airplane or a filter used in an automobile engine.

Further, a heat insulating sound absorbing material in which a planar material mixed with a binder is matted has been proposed. More specifically, for example, a heat-resistant resin binder is added to a planar material obtained by uniformly mixing inorganic fibers having high heat resistance and flame-retardant organic fibers having a thermal melting temperature or a thermal decomposition temperature of 350 DEG C or higher, A heat-insulating sound-absorbing material in which the whole is matted by heat treatment is disclosed. It is described that by using such a heat-insulating sound-absorbing material, it is possible to provide a heat-insulating sound-absorbing material having high safety due to high heat insulation and sound absorption.

Patent Document 1: Japanese Patent No. 4951507

However, although the heat-insulating sound-absorbing material described in Patent Document 1 is said to obtain a heat-insulating sound-absorbing material capable of bending having high heat insulating properties and sound-absorbing properties, strength is not sufficient because the fibers are bonded to each other with a binder. In particular, There is a problem that strength is lowered.

Further, in the case of a fiber structure in which fibers are bonded to each other via a binder, it is necessary to increase the amount of the binder in order to increase the strength, but if the content of the binder is increased, the content of the heat- There is a problem that compatibility is difficult.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a heat-resistant fiber structure having heat resistance and excellent strength such as bending stress and tensile strength.

In order to attain the above object, the heat-resistant fiber structure of the present invention is characterized in that the heat-resistant fibers are bonded to each other with a heat-resistant fiber having a glass transition temperature of 100 ° C or higher.

According to the present invention, it is possible to provide a heat-resistant fiber structure having heat resistance and excellent strength such as bending stress and tensile strength.

The heat-resistant fiber structure (hereinafter simply referred to as " fiber structure ") of the present invention is composed of a plurality of mutually bonded heat-resistant fibers. Unlike the conventional fiber structure, the fiber structure of the present invention has properties of having excellent heat resistance and strength by directly bonding the heat-resistant fibers without using a binder fiber having a low melting point.

The term " adhesion " as used herein refers to a state in which fibers are softened by heating so that the fibers are mutually deformed and engaged with each other at the intersections thereof, or the fibers are melted and integrated.

≪ Heat resistant fiber &

As the heat-resistant fiber constituting the fibrous structure, fibers having a glass transition temperature (T _g ) of 100 캜 or higher are used.

In general, a glass transition temperature (temperature at which a polymer starts micro molecular motion) is used as an index of heat resistance, but a resin having a glass transition temperature of 100 deg. C or higher is called an engineering plastic and is suitably used for applications requiring heat resistance Is used. The fiber using this resin as a raw material is called a heat-resistant fiber.

The heat-resistant fiber is a fiber which is softened by high-temperature superheated steam (150 DEG C to 600 DEG C) and can be self-adhered. Examples of the heat-resistant fiber include polyamide fiber, meta-aramid fiber, para- aramid fiber, melamine fiber, A polyimide fiber, a polyetherimide fiber, a polyetheretherketone fiber, a polyether ketone fiber, a polyether sulfone fiber, a polyether sulfone fiber, a polyether sulfone fiber, a polyether sulfone fiber, Ether ketone ketone fibers, and polyamideimide fibers. These fibers may be used singly or as a mixture of two or more kinds.

Of these fibers, polyamide fibers are preferably used from the viewpoints of low water absorption and chemical resistance, and it is preferable to use polyetherimide fibers from the viewpoint of flame retardancy and low flammability.

As the polyamide fiber, for example, a fiber composed of an aliphatic diamine and a semiaromatic polyamide which is a polyamide obtained from a dicarboxylic acid mainly composed of an aromatic component is used. The aliphatic diamine is represented by the following general formula (1), preferably n = 4 to 12, more preferably n = 6 and n = 9, and particularly preferably n =

The dicarboxylic acid mainly containing an aromatic component means that at least 60 mol% is an aromatic dicarboxylic acid. Preferred examples are terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and the like. A combination of an aliphatic diamine and an aromatic dicarboxylic acid is preferably a combination of an aliphatic diamine (n = 9 in the general formula (1)) and terephthalic acid.

In addition, polyether imide fiber is not having a melting point non-crystalline polyetherimide fiber is used, the glass transition, and may be a temperature above the 200 ℃ (T _g), three fineness even maintaining the heat resistance under high temperature conditions such as 200 ℃ . Such heat resistance can be judged by the dry heat shrinkage rate at 200 ° C. The amorphous polyetherimide fiber used as the heat resistant fiber of the present invention may have a dry heat shrinkage rate at 200 ° C. of 5.0% , It is preferable that the dry heat shrinkage ratio is -1.0 to 5.0%.

The amorphous polyetherimide-based fiber is also excellent in flame retardancy derived from a polymer. For example, the limiting oxygen index value (LOI value) may be 25 or more, preferably 28 or more, more preferably 30 or more .

The amorphous polyetherimide-based fiber may have a monofilament fineness of 15.0 dtex or less. From the viewpoints of production cost and handling property, it is more preferable that the monofilament fineness is 0.1 to 12.0 dtex and 0.5 to 10.0 dtex.

It is also preferable that the amorphous polyetherimide-based fiber has a fiber strength at room temperature of 2.0 cN / dtex or more. When the fiber strength is less than 2.0 cN / dtex, the processability at the time of making cloth such as paper or nonwoven fabric or cloth may be deteriorated, and the use of the fabric is restricted, which is not preferable. More preferably 2.3 to 4.0 cN / dtex, and 2.5 to 4.0 cN / dtex.

The cross-sectional shape (the cross-sectional shape perpendicular to the longitudinal direction of the fiber) of the heat-resistant fiber may be a circular cross section or a cross section having a deformed cross section (flattened, elliptical, polygonal, 3- to 14- Shaped, V-shaped, dog-bone (I-shaped), or the like), but may be a hollow sectional shape or the like.

The average fineness of the heat-resistant fibers can be selected in the range of, for example, 0.01 to 100 dtex, preferably 0.1 to 50 dtex, and more preferably 0.5 to 30 dtex (particularly 1 to 10 dtex), depending on the application. When the average fineness is in this range, a balance between the fiber strength and the adhesive property is excellent.

The average fiber length of the heat-resistant fibers can be selected, for example, in the range of 10 to 100 mm, preferably 20 to 80 mm, more preferably 25 to 75 mm (particularly 35 to 55 mm). When the average fiber length is within this range, the fibers are sufficiently entangled, so that the mechanical strength of the fiber structure is improved.

The crimp ratio of the heat-resistant fiber is, for example, 1 to 50%, preferably 3 to 40%, more preferably 5 to 30% (particularly 10 to 20%). Further, the number of crimps is, for example, 1 to 100 / inch, preferably 5 to 50 / inch, more preferably 10 to 30 / inch.

<Fiber structure>

The fiber structure of the present invention contains the above-mentioned heat-resistant fibers and has a structure in which the heat-resistant fibers are bonded to each other. The shape thereof can be selected depending on the application, but is generally sheet or plate.

Further, in order to have a nonwoven fabric structure having a high surface hardness and a bending hardness and having a balance of lightness and air permeability in the fabric structure of the present invention, the arrangement and bonding state of the fibers constituting the non- It needs to be adjusted. That is, it is preferable that the fibers constituting the fibrous web are arranged so as to intersect with each other while being arranged in parallel with the surface of the fibrous web (non-woven fiber).

Further, it is preferable that the fiber structure of the present invention is bonded at the intersection where the fibers cross each other. Particularly, a fibrous structure (molded article) requiring high hardness and strength may be formed into a bundle of several to several tens of bundle-shaped adhesive fibers in a state in which fibers other than the intersections are arranged substantially in parallel. These fibers are formed by partially forming a structure in which short fibers are intersected, points of intersection of bundle fibers or intersections of short fibers and bundled fibers are partially formed, whereby a structure of weaving "scrim" Or a structure in which fibers are adhered to each other at the intersection so as to confine adjacent fibers), so that desired bending behavior and surface hardness can be expressed. In the present invention, it is preferable that such a structure is distributed substantially uniformly along the surface direction and the thickness direction of the fiber web.

The term &quot; substantially parallel to the fiber web surface &quot; as used herein refers to a state in which a plurality of fibers locally are not repeatedly arranged along the thickness direction. More specifically, when an arbitrary cross section of the fiber web of the fiber structure is observed under a microscope, the presence ratio (number ratio) of fibers continuously extending in the thickness direction over 30% Refers to a state of 10% or less (particularly, 5% or less) with respect to a fiber.

The reason why the fibers are arranged in parallel to the fiber web surface is that if there are many fibers oriented along the thickness direction (direction perpendicular to the web surface), the fiber array is disturbed around the fibers, This is because the bending strength and surface hardness of the structure are reduced. Therefore, it is desirable to reduce this void as much as possible, and for this purpose, it is desirable to arrange the fibers as parallel to the fiber web as possible.

Particularly, when the fibrous structure of the present invention is a sheet or a plate-like molded body, when a load is applied in the thickness direction of the fibrous structure, if there is a large air gap, the air gap shrinks due to the load, Further, if this load is applied to the entire surface of the molded article, the thickness tends to be reduced as a whole. Therefore, if the fiber structure itself is made of a resin filling material having no voids, such a problem can be avoided. However, this results in a decrease in air permeability, making it difficult to break (bendability) and ensure lightness when bent.

On the other hand, in order to reduce the deformation in the thickness direction due to the load, it is conceivable to fill the fibers more densely by making the fibers thinner. However, if lightness and air permeability are secured only by the thin fibers, the stiffness of each fiber is lowered, The bending stress is lowered. In order to secure the bending stress, it is necessary to make the fiber diameter large to some extent. However, when a coarse fiber is simply mixed, large voids easily occur near the intersection of the coarse fibers, and the fiber becomes easily deformed in the thickness direction.

Therefore, the fibrous structure of the present invention has a structure in which the fibers are aligned and dispersed in parallel along the surface direction of the web (or the fiber direction is directed in a random direction) so that the fibers cross each other, Small pores are created to ensure light weight. Further, by continuing such a fiber structure, adequate air permeability and surface hardness are secured. Particularly, in the case where the bundle-type fibers bonded in parallel to each other in the longitudinal direction of the fiber are formed in a region that does not intersect with other fibers and is arranged in a generally parallel manner, a high bending strength can be secured mainly as compared with a case where the bundle- When a fibrous structure having a high hardness and a high strength is desired, it is preferable to form several bundle-shaped fibers at a portion where each fiber is arranged in a bundle form between the intersection and the intersection while bonding each fiber at an intersection desirable. Such a structure can be confirmed in the presence of short fibers when the end face of the molded article is observed.

In the fiber structure of the present invention, the fiber adhesion rate of the heat-resistant fiber by adhesion is preferably 10 to 85%, more preferably 25 to 75%, and even more preferably 40 to 65%.

If the fiber adhesion rate is less than 10%, there may be a problem that the hardness, bending stress and tensile strength are lowered. When the fiber adhesion rate is more than 85%, the voids between the fibers become small, There is a possibility that a problem that the weight and weight are reduced may occur. That is, by setting the fiber adhesion rate to 10 to 85%, the strength such as bending stress and tensile strength can be further improved without decreasing the lightweight property.

This fiber adhesion rate can be measured by the method described in the following Examples, and shows the ratio of the number of cross-sections of two or more bonded fibers to the total cross-section number of the nonwoven fiber cross-section. Therefore, the low fiber adhesion ratio means that the ratio of the plurality of fibers to each other (the ratio of the fiber to which the fibers are bundled) is small.

The heat-resistant fibers constituting the nonwoven fabric structure are bonded at the contact points of the respective fibers. However, in order to exhibit a large bending stress with a small number of contact points as possible, the heat- Center portion), and the back surface thereof. If the bonding point is concentrated on the surface or the inside, it is difficult not only to secure sufficient bending stress but also to lower the morphological stability in the portion where the bonding point is small. Therefore, from the viewpoint of further improving the bending stress without lowering the morphological stability, the fiber adhesion rate at the central portion (central portion) of the three regions divided into three in the thickness direction in the cross section in the thickness direction of the fiber structure is , It is preferable that both are in the above-mentioned range (10 to 85%).

It is preferable that the uniformity of the fiber bonding ratio in each region (i.e., the difference between the maximum value and the minimum value of the fiber bonding ratio) is not more than 20% (for example, 0.1 to 20% (For example, 0.5 to 15%) is more preferable, and 10% or less (for example, 1 to 10%) is more preferable.

The fiber structure of the present invention is excellent in hardness, bending strength, bending strength and toughness since the fiber bonding ratio has such uniformity in the thickness direction.

In the present invention, the term &quot; area divided into three in the thickness direction &quot; means each area divided into three by slicing in a direction orthogonal to the thickness direction of the plate-like fiber structure.

As described above, the fiber structure of the present invention is not only dyed and bonded with the heat-resistant fibers uniformly dispersed, but also can be densely bonded to the network structure at a short bonding distance (for example, several tens to several hundreds of 탆) Respectively. With this structure, even if an external force acts on the fiber structure of the present invention, the followability of deformation increases due to the flexibility of the fiber structure, and the external force is dispersed and reduced to each of the adhesion points of the finely dispersed fibers , High bending stress and tensile strength. On the other hand, in the conventional fiber structure in which the heat-resistant fibers are bonded to each other via the binder fibers, since the amount of the binder fibers is limited in order to secure heat resistance, the number of the bonding points is small and the amount of the binder fibers is increased to increase the bonding points It is difficult to obtain heat resistance and to uniformly disperse the adhesion of the fibrous structure in the thickness direction, so that deformation is liable to occur and it can be inferred that the bending stress and the tensile strength decrease.

In the fiber structure of the present invention, the frequency of occurrence of short fibers (short fiber end faces) in a cross section in the thickness direction is not particularly limited. For example, the presence frequency of staple fibers present in any 1 mm &lt; 2 &gt; of the cross section may be not less than 100 / mm 2 (for example, 100 to 300), but in particular, If required, the presence frequency of the short fibers is, for example, 100 pieces / mm 2 or less, preferably 60 pieces / mm 2 or less (for example, 1 to 60 pieces / Mm 2 or less (for example, 3 to 25 / mm 2). If the presence frequency of the short fibers is too large, the adhesion of the fibers is small and the strength of the formed body made of the fiber structure is lowered. If the frequency of existence of the short fibers is more than 100 pcs / mm &lt; 2 &gt;, adhesion of the fibers in a bundle shape becomes small, and it becomes difficult to secure a high bending strength. In the case of a plate-like molded article, it is preferable that the fibers adhered in a bundle shape are thin in the thickness direction of the molded article and have a wide width in the surface direction (longitudinal direction or width direction).

In the present invention, the frequency of occurrence of staple fibers is measured as follows. That is, in a scanning electron microscope (SEM) photograph of the end face of the molded article, a range equivalent to 1 mm 2 was observed, and the number of single fiber cross sections was counted. (For example, 10 randomly selected places) are observed in the photographs, and the average value per unit area of the short fiber cross-section is defined as the existence frequency of the short fibers. At this time, the number of fibers in a short fiber state is counted on the cross section. That is, in addition to the fibers having a completely short fiber state, even if several fibers are adhered to each other, the short fibers are separated from the adhesion portion of the cross section and counted as short fibers.

The heat-resistant fibers in the fiber structure can prevent loss of the fiber structure due to detachment of the fibers or the like because the both ends in the thickness direction are not connected (the fibers do not penetrate the fiber structure in the thickness direction). The production method for disposing the heat-resistant fibers in this manner is not particularly limited, but means for laminating a plurality of fiber-formed bodies entangled with heat-resistant fibers and bonding them with superheated steam is simple and reliable. Further, by adjusting the relationship between the fiber length and the thickness of the fiber structure, the fibers connecting both ends in the thickness direction of the fiber structure can be greatly reduced. From such a viewpoint, the thickness of the fiber structure is preferably 10% or more (for example, 10 to 1000%), preferably 40% or more (for example, 40 to 800% (For example, 60 to 700%), and more preferably 100% or more (for example, 100 to 600%). When the thickness and the fiber length of the fiber structure are in the above range, the mechanical strength such as the bending stress of the fiber structure is not lowered, and the loss of the fiber structure due to dropping of the fiber can be suppressed.

As described above, the density and the mechanical properties of the fiber structure of the present invention are influenced by the ratio or existence state of the bundle-type adhesive fibers. The fiber adhesion rate indicating the degree of adhesion can be easily measured based on the number of fiber cross-sections bonded in a predetermined region by taking a photograph of an enlarged cross section of the fiber structure using an SEM. However, when the fibers adhere to each other in a bundle shape, since each of the fibers adheres to each other in a bundle shape or at an intersection, especially when the density is high, it is likely to be difficult to observe as a single fiber.

In the present invention, as an index reflecting the degree of the fiber adhesion, the ratio of the area occupied by the cross section formed by the fibers and the bundle of bundles of fibers in the cross section (cross section in the thickness direction) of the fiber structure, It is possible. The fiber filling rate at the cross section in the thickness direction is, for example, 20 to 80%, preferably 20 to 60%, more preferably 30 to 50%. If the fiber filling rate is too small, the pores in the fabric structure become too large to secure the desired surface hardness and bending stress. On the contrary, if it is too large, the surface hardness and the bending stress can be sufficiently secured, but it becomes too heavy and the air permeability tends to be lowered.

The fibrous structure of the present invention (particularly, a fibrous structure having fibers bundled in a bundle shape and having short staple fibers of not more than 100 bundles / mm 2) is not limited to a plate shape (board shape) It is preferable to have a surface hardness that hardly causes deformation. As such an index, the hardness by the A type durometer hardness test (the test in accordance with JIS K 6253 "The hardness test of vulcanized rubber and thermoplastic rubber") is, for example, A50 or more, preferably A60 or more , More preferably A70 or more. If this hardness is too small, it is likely to be deformed by the load applied to the surface.

The fibrous structure containing the bundle-type adhesive fibers has a low frequency of occurrence of the bundle-type adhesive fibers and a high density of the fibers (bundled fibers and / or bundled fibers) in order to balance the bending strength, the surface hardness, Or staple fibers) at a high frequency. However, if the fiber adhesion rate is too high, the distance between the points to be bonded is too close to decrease the flexibility, and it becomes difficult to eliminate the deformation due to the external stress. Therefore, as described above, the fiber structure of the present invention preferably has a fiber adhesion rate of 85% or less. Since the fiber adhesion rate is not too high, it is possible to secure a passage by fine voids in the fiber structure, thereby improving lightness and air permeability. Therefore, in order to manifest a large bending stress, surface hardness and air permeability with a small number of contact points as possible, it is preferable that the fiber bonding rate is uniformly distributed along the thickness direction from the surface to the inside (center portion) Do.

Further, when the bonding point is concentrated on the surface or the inside, it becomes difficult to secure not only the bending stress and the dimensional stability but also the air permeability. Therefore, in the fiber structure of the present invention, it is preferable that the fiber bonding ratio of the center portion of the three regions (surface, center portion, and back surface) divided into three in the thickness direction in the cross section in the thickness direction is in the above- It is more preferable that both the central portion and the back surface are in the above-mentioned range. The difference between the maximum value and the minimum value of the fiber adhesion ratio in each region may be 20% or less (for example, 0.1 to 20%), preferably 15% or less (for example, 0.5 to 15% Is 10% or less (for example, 1 to 10%). In the present invention, when the fiber bonding ratio is uniform in the thickness direction, it is excellent in bending stress, tensile strength, bending resistance and toughness. The fiber bonding ratio of the present invention is measured by the method described in the following Examples.

The fiber structure of the present invention is also characterized in that it exhibits a bending behavior that can not be obtained with a conventional fiber structure in which heat-resistant fibers are bonded via binder fibers. In the present invention, in order to propose the bending behavior, the bending stress is measured at the repulsive force and the bending amount of the sample generated when the sample is gradually bent according to JIS K 7171 &quot; Method for obtaining plastic-bending property &quot; And used as an indicator of the behavior. That is, the larger the bending stress is, the more rigid the fibrous structure, and the more the bending amount (displacement) until the measurement object is broken, the more bending it is.

The fiber structure of the present invention has a bending stress in at least one direction (preferably all directions) of 0.05 MPa or more (for example, 0.05 to 100 MPa), preferably 0.1 to 30 MPa, more preferably 0.2 to 10 MPa MPa. If the bending stress is too small, it is easy to break due to its own weight or slight load when used as a board material. Also, if the bending stress is too large, it becomes too hard, and if it bends over the peak of the stress, it will bend and be easily broken. Further, in order to obtain hardness exceeding 100 MPa, it is necessary to increase the density of the fiber structure, and it becomes difficult to secure lightweightness.

The fiber structure of the present invention can ensure excellent lightweight property by the voids formed between the fibers. Unlike the foamed resin such as the sponge, these voids have air permeability because they are continuous and not independent voids. Such a structure is a structure that is difficult to manufacture by conventional hardening techniques such as a method of impregnating a resin or a method of densely adhering a surface portion to form a film structure.

That is, the fiber structure of the present invention has a low density, specifically, an apparent density of, for example, 0.03 to 0.7 g / cm 2, and in particular, for applications requiring lightweightness, for example, / Cm2, preferably 0.08 to 0.4 g / cm2, more preferably 0.1 to 0.35 g / cm2. In applications where hardness is required more than lightweight, the apparent density may be, for example, 0.2 to 0.7 g / cm 2, preferably 0.25 to 0.65 g / cm 2, more preferably 0.3 to 0.6 g / cm 2. When the apparent density is too low, it is lightweight, but it is difficult to sufficiently secure the bending hardness and the surface hardness. On the other hand, if the apparent density is too high, the hardness can be secured but the lightweight property is deteriorated. Further, when the apparent density is lowered, the fibers are entangled to come close to a general nonwoven fabric structure adhered at an intersection, while when the density is increased, the fibers adhere to each other in a bundle shape to form a structure close to the porous molded article.

The term &quot; apparent density &quot; as used herein refers to the density calculated according to the surface density and the thickness measured according to the standard of JIS L 1913 (general nonwoven fabric test method).

The area density of the fiber structure of the present invention can be selected from the range of, for example, about 50 to 10000 g / m 2, preferably about 150 to 8000 g / m 2, and more preferably about 300 to 6000 g / m 2. For applications requiring hardness more than lightweight, the surface density may be, for example, about 1000 to 10000 g / m 2, preferably about 1500 to 8000 g / m 2, and more preferably about 2000 to 6000 g / m 2. If the area density is too small, it is difficult to ensure hardness. If the area density is too large, the web is too thick, so that superheated steam does not sufficiently enter the inside of the web in the processing by superheated steam, making it difficult to obtain a uniform fiber structure in the thickness direction .

When the fibrous structure of the present invention is in the form of a plate or a sheet, its thickness is not particularly limited, but may be selected within the range of about 1 to 100 mm, and is, for example, 2 to 50 mm, preferably 3 to 20 mm Mm, and more preferably 5 to 150 mm. If the thickness is too thin, it becomes difficult to secure the hardness. If the thickness is too large, the mass becomes too heavy.

The fiber structure of the present invention has a nonwoven fabric structure, and thus has high air permeability. The air permeability of the fibrous structure of the present invention is 0.1 cm 3 / cm 2 / sec or more (for example, 0.1 to 300 cm 3 / cm 2 / sec), preferably 0.5 to 250 cm 3 / Cm2 / sec (for example, 1 to 250 cm3 / cm2 / sec), more preferably 5 to 200 cm3 / cm2 / sec, and generally 1 to 100 cm3 / cm2 / sec. If the air permeability is too small, it is necessary to externally apply pressure to pass the air through the fabric structure, making natural air entry difficult. On the other hand, if the air permeability is too large, the air permeability is high, but the fiber voids in the fiber structure become too large, and the bending stress is lowered.

Since the fiber structure of the present invention has a nonwoven fabric structure, it has a high heat insulating property and a low thermal conductivity of 0.1 W / m · K or less, for example, 0.03 to 0.1 W / m · K, preferably 0.05 to 0.08 W / M · K.

Next, a method for manufacturing the fiber structure of the present invention will be described.

In the method for producing a fiber structure according to the present invention, first, the above-mentioned heat-resistant fiber is made into a web. Examples of the web forming method include a direct method such as a tolerance method, such as a spunbond method and a meltblown method, a carding method using meltblown fibers or staple fibers, and a dry method such as an airlay method. Among these methods, a carding method using meltblown fibers or staple fibers, in particular, a carding method using staple fibers, is generally used. Webs obtained using staple fibers include, for example, a random web, a semi-random web, a parallel web, a cross-lab web, and the like. When the proportion of the bundle-type adhesive fibers in the web is increased, a semi-random web or a parallel web is preferable.

In the step of adhering the fibers of the obtained fiber web, the means for adhering the fibers may be conventional hot air treatment or hot pressing, or the fibers may be bonded together by superheated steam. In the case of using superheated steam, the fibrous web obtained in the above process is sent to the next process by a belt conveyor and is exposed to the superheated steam (high-pressure steam) stream to obtain a fibrous structure having the nonwoven fabric structure of the present invention. That is, the fibrous web conveyed by the belt conveyor passes through the superheated vapor stream ejected from the nozzle of the steam injection apparatus, and the heat-resistant fibers are three-dimensionally adhered (thermally adhered) by the superheated steam injected.

By heat treatment by such superheated steam (150 DEG C to 600 DEG C), the heat-resistant fibers are adhered to each other to obtain a network of fibers, so that even the inside of the thickness direction of the fiber structure can be uniformly processed.

Here, the temperature of the superheated steam injected into the heat-resistant fibers is preferably in the range of 150 to 600 캜. If the temperature is lower than 150 ° C, the energy imparted to the heat-resistant fibers may be insufficient, resulting in insufficient adhesion between the fibers. If the temperature is higher than 600 ° C, the energy transferred to the fibers close to the jetting apparatus becomes too large, This is because there is a possibility that the property is deteriorated.

The belt conveyor to be used is not particularly limited as long as it can be processed by superheated steam while basically compressing the fiber web used for processing to a target density and an endless conveyor is suitably used. Further, the belt conveyor may be a general single belt conveyor, or two belt conveyors may be combined as needed, and the web may be sandwiched between the both belts. As a result, it is possible to suppress the problem of deforming the shape of the web conveyed due to the external force such as superheated steam or conveyor vibration used in the processing when the web is processed. It is also possible to control the density and thickness of the nonwoven fabric after the treatment by adjusting the interval of the belt.

Steam injectors for supplying superheated steam to the web, when combined with two belt conveyors, are mounted in one conveyor and supply superheated steam to the web through a conveyor net. A suction device may be mounted on the opposite conveyor. The excess superheated steam passing through the web can be sucked and discharged by the suction device. Further, in order to simultaneously treat both the front and rear sides of the web by the superheated steam, a suction device is further provided downstream of the conveyer to which the overheated steam sprayer is mounted, and the suction device is mounted in the opposite conveyor Superheated steam injection device may be provided. In the absence of a superheated steam jetting device and a suction device in the downstream, steam treatment before and after the fiber web can be replaced by reversing the front and back of the once treated fiber web and passing the same through the treatment device again.

The endless belt used in the conveyor is not particularly limited as long as it does not interfere with conveyance of the web or superheated steam treatment. However, in the case of superheated steam treatment, the surface shape of the belt may be transferred to the surface of the fibrous web according to the conditions, and therefore, it is preferable to suitably select it depending on the application. Particularly, in the case of a fiber structure having a flat surface, a fine mesh is used. Further, the upper limit of the 90 mesh is the upper limit, and the mesh having the lower mesh has a lower air permeability, making it difficult for the steam to pass through. From the viewpoints of heat resistance to superheated steam treatment, the material of the mesh belt is preferably selected from the group consisting of a metal, a heat-treated polyester resin, a polyphenylene sulfide resin, a polyarylate resin (wholly aromatic polyester resin) And a heat resistant resin such as a polyamide-based resin.

Since the superheated steam injected from the steam injector is an air stream, unlike the water flow coupling treatment or the needle punching treatment, the steam enters the web without largely moving the fibers in the web to be treated. It is considered that the superheated steam flow effectively coats the surface of each heat-resistant fiber existing in the web in the superheated state by the action of the steam flow into the web and the superheating action, and uniform heat bonding becomes possible. Since this treatment is carried out in a very short time under a high speed air flow, the heat conduction to the fiber surface of the superheated steam is sufficient, but the treatment is completed before the heat conduction to the inside of the fiber is sufficiently performed. It is difficult to cause the entire fiber web to be shrunk to be shrunk and deformation that may interfere with the thickness thereof. As a result, thermal bonding is completed so that the fiber web does not undergo large deformation and the degree of adhesion in the surface and thickness direction is substantially uniform.

Further, in the case of obtaining a fibrous structure having a high surface hardness and a high bending strength, when the superheated steam is supplied to the web and treated, the treated web is conveyed between the conveyor belt and the roller at a target apparent density (for example, 0.03 To 0.7 g / cm &lt; 3 &gt;). In particular, in order to obtain a relatively high density fiber structure, it is necessary to compress the fiber web with sufficient pressure when treating with superheated steam. It is also possible to secure a proper clearance between the rollers or between the conveyors to adjust the thickness or the density to a desired level. In the case of a conveyor, it is preferable to set the tension of the belt as high as possible, and gradually narrow the clearance upstream of the vapor treatment point, since it is difficult to compress the web at one time. Further, by adjusting the steam pressure and the treatment speed, the fiber structure is processed to have desired bending hardness, surface hardness, light weight, and air permeability.

At this time, when it is desired to increase the hardness, if the back side of the endless belt opposite to the nozzle with the web therebetween is made of a stainless steel plate or the like so that the steam can not pass therethrough, So that it is more firmly adhered by the effect of warming of steam. On the other hand, when light adhesion is required, a suction device may be disposed to discharge extra steam to the outside.

The nozzle for spraying the superheated steam may be arranged by using a plate or a die in which predetermined orifices are continuously arranged in the width direction and arranging the orifices in the width direction of the supplied web. The orifice column may be at least one column, or may be an array in which a plurality of columns are arranged side by side. Further, a plurality of nozzle dies having one row of orifice columns may be provided in parallel.

When a nozzle of the type having an orifice formed on the plate is used, the thickness of the plate may be 0.5 to 1 mm. The diameter or pitch of the orifice is not particularly limited as long as the fiber can be fixed in a desired manner, but the diameter of the orifice is generally 0.05 to 2 mm, preferably 0.1 to 1 mm, 0.5 mm. The pitch of the orifices is generally 0.5 to 3 mm, preferably 1 to 2.5 mm, and more preferably 1 to 1.5 mm. If the diameter of the orifice is too small, the accuracy of machining of the nozzle is lowered, and there is a problem in equipment that processing becomes difficult and a problem in operation that clogging easily occurs. On the other hand, if it is too large, the steam jetting force is lowered. On the other hand, if the pitch is too small, the nozzle hole becomes too tight, so that the strength of the nozzle itself is lowered. On the other hand, if the pitch is too large, the high-temperature steam may not sufficiently reach the web, and the strength of the web is lowered.

The superheated steam is not particularly limited as long as heat-resistant fiber fixing can be achieved. The superheated steam can be set depending on the material and the shape of the fiber to be used, but the pressure is, for example, 0.1 to 2 MPa, preferably 0.2 to 1.5 MPa, More preferably 0.3 to 1 MPa. If the pressure of the steam is too high or too strong, there is a possibility that the fibers forming the web will flow and cause deformation of the base, or the fibers will become too melted to be able to partially retain the fiber shape. If the pressure is too low, the amount of heat required for bonding the fibers can not be imparted to the web, or superheated steam can not penetrate through the web, resulting in a fiber adhesive layer in the thickness direction. Thus, May become difficult.

The fibrous structure having the nonwoven fabric structure thus obtained has low density, high bending stress and surface hardness, which are the same as those of a general nonwoven fabric, and has heat resistance as well as air permeability, sound absorbing property and heat insulating property. Therefore, by using such a performance, it can be applied to applications requiring heat resistance such as automobile interior material, inner wall of an aircraft, building material board, and the like.

Example

Hereinafter, the present invention will be described on the basis of examples. It should be noted that the present invention is not limited to these examples, and these examples can be modified or changed based on the object of the present invention, and they are not excluded from the scope of the present invention.

The physical properties of the examples were measured by the following methods. In the examples, &quot; part &quot; means mass part and &quot;% &quot; means mass%.

(Example 1)

&Lt; Fabrication of Fiber Structure &gt;

Resistant fiber using a semi-aromatic polyamide resin (trade name: Genesta, melting point: 265 占 폚, glass transition temperature: 125 占 폚, thermal decomposition temperature: 400 占 폚) made of a diamine having 9 carbon atoms and terephthalic acid (Fineness: 1.7 dtex, fiber length: 51 mm). Next, using this heat-resistant fiber, a carding web having a surface density of 50 g / m &lt; 2 &gt; was produced by the carding method, and 12 webs were superimposed to make a carding web having a total area density of 600 g / m &lt; 2 &gt;. The carding web was transferred to a belt conveyer equipped with a 50 mesh stainless steel endless net having a width of 500 mm.

The belt conveyor is composed of a pair of a lower conveyor and a pair of upper conveyors, and a vapor jet nozzle is provided on the belt back side of at least one of the conveyers. In addition, superheated steam can be injected into the web passing through the belt. Further, on the upstream side of the nozzle, a web roll thickness adjusting metal roll (hereinafter sometimes abbreviated as &quot; web thickness adjusting roll &quot;) is provided on each conveyor. The lower conveyor has a flat upper surface (that is, a surface through which the web passes), while the upper conveyor has a shape in which the lower surface is bent along the web thickness adjusting roll, and the web thickness adjusting roll of the upper conveyor is formed of a web And is arranged to be paired with the thickness adjusting roll.

In addition, the upper conveyor is movable up and down, so that the rolls for adjusting the web thickness of the upper conveyor and the lower conveyor can be adjusted at a predetermined interval. The upstream side of the upper conveyor is bent at a 30 degree angle relative to the downstream portion with respect to the web thickness adjusting roll (relative to the downstream side of the upper conveyor), and the downstream portion is bent so as to be parallel to the lower conveyor. Further, when the upper conveyor moves up and down, it moves while maintaining this parallel relationship.

Each of these belt conveyors is rotatable in the same direction at the same speed and has a structure in which both the conveyor belts and the web thickness adjusting rolls can be pressed while maintaining a predetermined clearance. This is to work like a so-called calender process to adjust the web thickness before steam treatment. That is, the carding web conveyed from the upstream side runs on the lower conveyor, but gradually narrows the interval from the upper conveyor until reaching the web thickness adjusting roll. Then, when this gap is narrower than the web thickness, the web is sandwiched between the upper and lower conveyor belts and travels while being compressed gradually. The web is compressed until the thickness becomes almost equal to the clearance provided in the web thickness adjusting roll, superheated steam treatment is performed in the thickness state, and thereafter, the web travels while maintaining the thickness at the downstream portion of the conveyor. Here, the roll for adjusting the web thickness was adjusted to have a linear pressure of 50 kg / cm.

Subsequently, the carding web was introduced into the steam injecting apparatus provided in the lower conveyor, and this apparatus was sprayed with steam (vertically) so that the superheated steam of 300 ° C passed through the carding web in the thickness direction thereof, Fiber structure was obtained. This steam jetting device is provided with a nozzle in the lower conveyor for jetting the super heated steam through the conveyor net toward the web, and a suction device is installed in the upper conveyor. In addition, on the downstream side of the web advancing direction of the jetting apparatus, a combination jetting device in which the arrangement of the nozzles and the suction device is reversed is installed, and superheated steam is applied to both the front and rear surfaces of the web.

Further, the steam injection nozzle has a hole diameter of 0.3 mm, and the nozzles are arranged in a row at a pitch of 1 mm along the width direction of the conveyor. The processing speed was 3 m / min, and the distance (distance) between the nozzle side and the upper and lower conveyor belts on the suction side was 5 mm. The nozzles were disposed on the back side of the conveyor belt so as to be substantially in contact with the belt.

&Lt; Measurement of surface density &

(G / m &lt; 2 &gt;) of the fabric structure produced in accordance with JIS L 1913 was measured. Table 1 shows the above results.

&Lt; Measurement of apparent density &

The thickness (mm) of the fabric structure produced in accordance with JIS L 1913 was measured, and the apparent density (g / cm 3) was calculated based on the value of the thickness and the area density. Table 1 shows the above results.

&Lt; Measurement of fiber adhesion rate &

Using a scanning electron microscope (SEM), a cross section of the fiber structure was photographed at a magnification of 100 times. Next, a cross-sectional photograph in the thickness direction of the taken-up fiber structure is divided into three equal parts in the thickness direction, and the number of recognizable fiber cross-sections (fiber cross-section) in each of the three regions (front side, The ratio of the number of cut surfaces to which the fibers adhered was determined.

More specifically, the percentage of the total number of cross-sectional areas of fibers recognized in each area occupied by the number of cross-sections in a state where two or more fibers are bonded is expressed as a percentage based on the following formula (1).

The portion where the fibers come into contact with each other has a portion which is simply contacted but does not adhere and a portion which is adhered by adhesion. However, since the fiber structure is cut for photographing the microscope, Depending on the stress, the fibers in contact simply separated. Therefore, in the cross-sectional photograph, it is assumed that the fibers in contact with each other are bonded.

For each photograph, all the fibers capable of confirming the cross-section were counted. When the number of fibers was 100 or less, the photographs were observed so that the total cross-sectional area of the fibers exceeded 100. Further, the fiber adhesion rates were obtained for each of the three regions, and the difference between the maximum value and the minimum value (i.e., uniformity) was also obtained. Table 1 shows the above results.

&Lt; Measurement of bending stress &

A test piece (10 mm in width and 100 mm in length) was prepared from the manufactured fiber structure in accordance with JIS K 7171 (Method for obtaining plastic-bending characteristics), and the distance between points was 80 mm and the test speed was 10 mm / , And the bending stress (MPa) was measured. Table 1 shows the above results.

&Lt; Measurement of tensile strength &

A test piece (30 mm in width and 150 mm in length) was prepared from the prepared fabric structure in accordance with the provisions of JIS L 1913 (general nonwoven fabric test method), and the bite interval was 100 mm and the test speed was 10 mm / Tensile strength (N / 30 mm) was measured. Table 1 shows the above results.

(Example 2)

&Lt; Fabrication of Fiber Structure &gt;

(Glass transition temperature: 215 占 폚, thermal decomposition temperature: 540 占 폚, fineness: 8.9 dtex, fiber length: 51 mm) as heat-resistant fibers were prepared. Next, using this heat-resistant fiber, a carding web having a surface density of 100 g / m &lt; 2 &gt; was prepared by the carding method and formed into a sheet using a water flow bonding method.

Next, after ten sheets were laminated, the laminate was transferred to a belt conveyer equipped with a stainless steel endless net of 50 mesh and a width of 500 mm.

Next, a carding web is introduced into the steam injector provided in the lower conveyor as in the above-described first embodiment, and the superheated steam at 330 ° C is injected (perpendicularly) so as to pass through the carding web in the thickness direction Steam treatment was carried out to obtain a fibrous structure having the nonwoven fabric structure of this example.

Next, as in the above-described Example 1, surface density measurement, apparent density measurement, fiber adhesion rate measurement, bending stress measurement, bending load measurement, and tensile strength measurement were performed. Table 1 shows the above results.

(Example 3)

&Lt; Fabrication of Fiber Structure &gt;

Nine carding webs used in Example 1 were laminated and heat-pressed at 260 占 폚 for 1 minute by a hot press apparatus to obtain a fibrous structure.

Next, as in the above-described Example 1, measurements of surface density, apparent density, fiber adhesion rate, bending stress, bending load, and tensile strength were carried out. Table 1 shows the above results.

(Comparative Example 1)

&Lt; Fabrication of Fiber Structure &gt;

(Semi-aromatic polyamide fiber prepared in Example 1) and polypropylene / polyethylene core-sheath type conjugated fiber (HR-NTW made by Ube Industries, Inc., glass transition temperature of the core part: -20 占 폚, glass transition temperature of the beginning part: -120 deg. C, pyrolysis temperature at the deep portion: 240 deg. C, pyrolysis temperature at the initial portion: 270 deg. C, fineness: 1.7 dtex, fiber length: 51 mm) was prepared and mixed at a mass ratio of 80/20. Next, a carding web having a surface density of 50 g / m &lt; 2 &gt; was prepared by carding using this mixed fiber, and six webs were superimposed to form a carding web having a total area density of 300 g / m &lt; 2 &gt;. The carded web was heat-treated at 150 ° C for 1 minute by a hot-air dryer to obtain a fiber structure of this comparative example.

Next, as in the above-described Example 1, surface density measurement, apparent density measurement, fiber adhesion rate measurement, bending stress measurement, bending load measurement, and tensile strength measurement were performed. Table 1 shows the above results.

As shown in Table 1, the fibrous structures of Examples 1 to 3 in which the heat-resistant fibers having a glass transition temperature of 100 占 폚 or more were thermally bonded were found to have higher thermal conductivity than the fibrous structure of Comparative Example 1 in which the heat- , Bending stress and tensile strength. Particularly, the fibrous structures of Examples 1 and 2, in which the fiber adhesion rate is high, are significantly higher in bending stress and tensile strength than Comparative Example 1, and are superior in strength.

In addition, in the fibrous structures of Examples 1 and 2, the tensile strength retention (tensile strength at 180 캜 / tensile strength at room temperature) is much higher than that of Comparative Example 1, and the heat resistance is excellent.

Further, as shown in Table 1, the bending stress of the fabric structure of Comparative Example 1 is 0, the fabric structure is weak enough to warp by its own weight, and the bending stress is below the measurement limit. For example, The handleability is degraded because it is sagged without following the wall surface or the ceiling scene. On the other hand, the bending stress of Example 3 is 0.4 MPa, which is superior to that of Comparative Example 1 and can be applied without hanging on the wall surface if it has a bending stress of about 0.4 MPa. .

In addition, the fibrous structure of Example 3 has a higher tensile strength retention (tensile strength at 180 ° C / tensile strength at normal temperature) than Comparative Example 1 and excellent heat resistance.

On the other hand, in Comparative Example 1, since the fibers are bonded to each other with a binder, as shown in Table 1, the fiber adhesion rate is remarkably lowered. As a result, compared with Examples 1 and 2, bending stress and tensile strength It can be said that it has been significantly lowered.

INDUSTRIAL APPLICABILITY As described above, the present invention is suitable for a heat-resistant fiber structure constituted by heat-resistant fibers and used as a heat insulating material and a sound-absorbing material.

Claims (5)

A fiber structure comprising a heat-resistant fiber having a glass transition temperature of 100 DEG C or higher,
And the heat-resistant fibers are bonded to each other. The method according to claim 1,
Wherein the heat-resistant fiber has a fiber adhesion rate of 10 to 85%. The method according to claim 1 or 2,
A heat-resistant fibrous structure having a fiber bonding ratio at a central portion of 10 to 85% out of three regions divided into three in the thickness direction at a cross section in the thickness direction of the fibrous structure. The method according to claim 2 or 3,
And the uniformity of the fiber bonding ratio is 20% or less. The method according to any one of claims 1 to 4,
A heat-resistant fiber structure having an apparent density of 0.03 to 0.7 g / cm3.